Transmitter for an electrical speedometer



Sept. 14, 1965 D. A. HAASE TRANSMITTER FOR AN ELECTRICAL srmnommnn Filed March 28, 1962 2 Sheets-Sheet 2 ro 4 2 O 2 4 f0 8 INVENTOR. DONALD A HA ASE Fig.4

A TTORNEY United States Patent 3,206,667 TRANSMITTER FOR AN ELECTRICAL SPEEDOMETER Donald A. Haase, Rochester, N.Y., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed Mar. 28, 1962, Ser. No. 183,067 13 Claims. (Cl. 321-50) This invention pertains to electric transmitters for speedometer drives, and particularly to an improved switch-type voltage inverter for converting direct current to three phase alternating current.

Heretofore, commutator-type electric transmitters have been devised for use in electric speedometer drives, one form of electric transmitter being disclosed in copending application Serial No. 857,012, filed December 3, 1959, in the name of Fritz et al., and assigned to the assignee of this invention, now Patent No. 3,108,216. Commutator-type inverters comprise a stationary commutator and a revolving brush drum and thus tend to be rather large in over-all dimension. The present invention relates to a switching-type converter and thus enables the size to be reduced to significant extent. Accordingly, among my objects are the provision of an improved transmitter for converting direct current into three phase alternating current; the further provision of an electric transmitter embodying a rotatable cam and a plurality of movable switch blades; and the still further provision of an electric transmitter embodying a grooved rotatable cam for actuating followers attached to the movable switch blades.

The aforementioned and other objects are accomplished in the present invention by attaching one end of the movable switch blades to terminals and attaching cam follower pins to the other ends of the movable switch blades, the cam follower pins riding in a cam groove formed in the cam plate. Specifically, the improved electric transmitter comprises a die cast housing which is connected to one terminal of the vehicle battery and carries a cover of insulating material. The die cast housing carries three leaf spring blades, and the cover has three output terminals and a center input terminal which carries a contact ring disposed within the housing. The movable leaf switch blades have their outer ends attached to the three terminals and have axially extending can follower pins attached to their inner ends. Intermediate their ends, the movable leaf switch blades carry a pair of longitudinally offset, oppositely extending contacts, the outer contacts of which are engageable with the relatively stationary leaf spring switch blades, and the inner contacts of which are engageable with the contact ring.

The follower pins on the movable leaf spring blades engage a groove in a cam plate rotatably journalled in the housing, the cam plate being composed of insulating material. The cam groove deflect the three movable leaf switch blades sequentially into contact with the relatively stationary switch blades and the contact ring at a frequency twice the rotational speed of the cam plate to obtain two complete electrical cycles for each mechanical cycle, and thus enable a four pole synchronous receiver motor to rotate at the same speed as the mechanical input speed to the transmitter.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings, wherein a preferred embodiment of the present invention is clearly shown.

In the drawings:

FIGURE 1 is an end view with certain parts broken away, partly in section and partly in elevation, of the improved transmitter.

3,206,667 Patented Sept. 14, 1965 ice FIGURE 2 is a fragmentary longitudinal sectional view taken along line 22 of FIGURE 1.

FIGURE 3 is a sectional view taken along line 3-3 of FIGURE 2.

FIGURE 4 is a graph of the three phase staircase signal produced by the transmitter.

With particular reference to FIGURES 1 through 3, the transmitter comprises a metal die cast housing 10 having a cup-shaped recess and carrying a sleeve bearing 12 for journalling a cam plate 14 of insulating material. It is to be understood that the cam plate 14 is driven from a suitable power takeolf at a speed proportional to vehicle road speed. Moreover, the die cast housing 10 is electrically grounded to the chassis of the vehicle and is thus connected to one terminal of the vehicle battery.

As seen particularly in FIGURES 1 and 3, the insulative cam plate 14 is formed with an endless face cam groove 16 which receives three follower pins 18, 20 and 22 that project axially from the inner ends of the leaf spring blades 24, 26 and 28, respectively. The outer ends of the leaf spring blades 24, 26 and 28 are mechanically and electrically connected to three circumferentially spaced output terminals 30, 32 and 34, respectively, which are molded in an insulative cover 36 which closes the open end of the cup-shaped housing 10, and is suitably secured thereto. A centrally arranged input terminal 38 is also molded in the cover 36, the input terminal 38 being electrically connected to a coaxially arranged contact ring 40 disposed within the housing 10. The terminal 38 is connected to the other terminal of the battery thus completing the input electrical circuit.

Three relatively stationary leaf spring blades 42, 44 and 46 have their outer ends attached to bosses 48 of the housing 10, and thus are electrically grounded. The leaf spring blades 42, 44 and 46 carry contacts 50, 52 and 54 at their outer ends. The movable leaf spring blades 24, 26 and 28 each carry a pair of oppositely extending, offset contacts, as shown in FIGURE 3. Thus, the leaf spring blade 24 carries contacts 56 and 58; the leaf spring blade 26 carries contacts 60 and 62; and the leaf spring blade 28 carries contacts 64 and 66. The innermost radial contacts 58, 62 and 66 are adapted to engage the contact ring 40, while the outermost radial contacts 56, 60 and 64 are adapted to engage the relatively stationary contacts 50, 52 and 54, respectively.

It is to be understood that only the cam plate 14 rotates, and in so rotating the leaf spring blades 24, 26 and 28 will be deflected sequentially by the cam grooves 16 through their follower pins 18, 20 and 22, respectively, into and out of engagement with the contacts on the relatively stationary leaf spring blades and with the contact ring 40. Contact pressure between the contacts 56, 60 and 64 and the contacts 50, 52, and 54, respectively, is obtained by bending, or deflecting, the respective leaf spring blades 42, 44 and 46 radially outward. Contact pressure of the contacts 58, 62 and 64 with the contact ring 40 is obtained by bending, or deflection, of the leaf spring blades 24, 26 and 28, respectively. It will also be observed that the cam groove 16 is composed of two diametrically opposed, symmetrical halves, and thus during each mechanical revolution of the cam plate 14, the respective movable contacts will be actuated throughout two complete cycles, and thus the alternating electric signal generated will have an electrical frequency twice that of the mechanical frequency of the cam plate 14.

Referring to FIGURE 4, the transmitter converts direct current battery voltage into a three phase staircase signal having a wave form as shown in the graph. It will be understood that the three output terminals 30, 32 and 34 are connected to the three phase Y connected coils of the synchronous receiver motor, and the wave forms shown in FIGURE 4 are those appearing across the three coils of the receiver.

Thus, each of the three terminals 30, 32 and 34 can be connected to positive, negative or zero potential. In each instance the input to each coil of the receiver is at zero potential for thirty electrical degrees (fifteen mechanical degrees rotation of the cam plate); then at a positive potential for 150 electrical degrees; zero potential for thirty electrical degrees; and negative potential for 150 electrical degrees to complete the 360 electrical degree cycle. A complete 360 electrical cycle requires only 180 mechanical movement of the brush plate 14 as alluded to hereinbefore.

While the embodiment of the invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted.

What is claimed is as follows:

1. A transmitter for an electric speedometer including, a plurality of circumferentially spaced stationary switch contacts, a like number of circumferentially spaced movable switch contacts, a stationary contact ring, a source of direct current connected between said stationary switch contacts and said contact ring, and rotatable cam means engageable with said movable switch contacts for sequentially deflecting said movable switch contacts into and out of engagement with said stationary switch contacts and said contact ring to produce an alternating current signal having a frequency proportional to the rotative speed of said cam means.

2. A transmitter for an electric speedometer including, a plurality of circumferentially spaced stationary switch contacts, a contact ring, a like number of circumferentially spaced movable switch contacts disposed therebetween, a source of direct current connected between said stationary switch contacts and said contact ring, and rotat able cam means for sequentially deflecting said movable switch contacts into and out of engagement with said stationary switch contacts and said contact ring to produce an alternating current signal having a frequency twice the speed of rotation of said cam means.

3. A transmitter for an electric speedometer including, a housing having a cup-shaped recess, a cover closing the open end of said cup-shaped recess, a plurality of circumferentially spaced stationary switch contacts mounted on said housing, a like number of circumferentially spaced movable switch contacts mounted on said cover, a contact ring mounted on said cover, said contact ring being connectible to one terminal of a direct source of electric current, said stationary switch contacts being connectible to the other terminal of the source of direct current, and rotatable cam means journalled in said housing for sequentially deflecting said movable switch contacts into and out of engagement with said stationary switch contacts and said contact ring to produce an alternating current signal having a frequency proportional to the rotative speed of said cam means.

4. A transmitter for an electric speedometer including, a housing having a cup-shaped recess, a cover closing said recess, a plurality of circumferentially spaced, stationary leaf spring blades attached to said housing and carrying contacts at their outer ends, a like number of circumferentially spaced movable leaf spring blades attached to said cover disposed radially inward of said stationary leaf spring blades and carrying contact means intermediate their ends, a centrally arranged contact ring carried by said cover, and rotatable cam means journalled in said housing and engageable with said movable leaf spring blades for sequentially deflecting the same so that the contact means thereof sequentially engage the contacts of said stationary leaf spring blades and said contact ring to produce an alternating current signal having a frequency proportional to the rotative speed of said cam means.

5. The transmitter set forth in claim 4 wherein the contact means on said movable leaf spring blades comprises a pair of longitudinally offset contacts disposed on opposite sides of each leaf spring blade.

6. The transmitter set forth in claim 5 wherein said rotatable cam means comprises a plate having a cam groove in the face thereof.

7. The transmitter set forth in claim 6 wherein each movable leaf spring blade has an axially extending follower pin disposed in said cam groove.

8. The transmitter set forth in claim 4 wherein said movable leaf spring blades deflect said stationary leaf spring blades to obtain the requisite contact pressure.

9. The transmitter set forth in claim 4 wherein said movable leaf spring blades are deflected by engagement with said contact ring to obtain the requisite contact pressure.

10. The transmitter set forth in claim 4 including a plurality of output terminals carried by said cover, each output terminal being electrically connected to one of said movable leaf spring blades.

11. A transmitter including, a plurality of circumferentially spaced movable contacts, a like number of circumferentially spaced stationary contacts located radially outward of said movable contacts, stationary contact means disposed radially inward of said movable contacts, a source of direct current connected between said stationary contacts and said stationary contact means, and rotatable cam means engageable with said movable contacts for sequentially deflecting said movable contacts into and out of engagement with said stationary contacts and said stationary contact means to produce an alternating current signal having a frequency proportional to the rotative speed of said cam means.

12. A transmitter including, a housing assembly comprising a housing having a cup-shaped recess and a cover attached to said housing and closing said recess, said cover being composed of insulating material, a plurality of circumferentially spaced movable contacts attached to said cover, a like number of circumferentially spaced stationary contacts mounted in said housing assembly radially outward of said movable contacts, stationary contact means supported in said cover and located radially inward of said movable contacts, said stationary contacts being connectible to one terminal of a source of direct current, said stationary contact means being connectible to the other terminal of the source of direct current, and a rotatable cam journalled in said housing assembly for sequentially deflecting said movable contacts into and out of engagement with said stationary switch contacts and said stationary contact means to produce an alternate current signal having a frequency proportional to the rotative speed of said cam.

13. A transmitter including, a plurality of circumferentially spaced movable contacts, first stationary con tact means disposed radially outward of said movable contacts, second stationary contact means disposed radially inward of said movable contacts, a source of direct current connected between said first and second stationary contact means, and rotatable cam means engageable wifh said movable contacts for sequentially deflecting said movable contacts into and out of engagement with said first and second stationary contact means to produce a polyphase alternating current signal having a frequency proportional to the rotative speed of said cam means.

References Cited by the Examiner UNITED STATES PATENTS 2,651,750 9/53 Koppelmann et al. 321-48 FOREIGN PATENTS 566,471 1/ 45 Great Britain. 691,823 6/40 Germany. 960,698 3/57 Germany.

LLOYD MCCOLLUM, Primary Examiner. 

4. A TRANSMITTER FOR AN ELECTRIC SPEEDOMETER INCLUDING, A HOUSING HAVING A CUP-SHAPED RECESS, A COVER CLOSING SAID RECESS, A PLURALITY OF CIRCUMFERENTIALLY SPACED, STATIONARY LEAF SPRING BLADES ATTACHED TO SAID HOUSING AND CARRYING CONTACTS AT THEIR OUTER ENDS, A LIKE NUMBER OF CIRCUMFERENTIALLY SPACED MOVABLE LEAF SPRING BLADES ATTACHED TO SAID COVER DISPOSED RADIALLY INWARD OF SAID STATIONARY LEAF SPRING BLADES AND CARRYING CONTACT MEANS INTERMEDIATE THEIR ENDS, A CENTRALLY ARRANGED CONTACT RING CARRIED BY SAID COVER, AND ROTATABLE CAM MEANS JOURNALLED IN SAID HOUSING AND ENGAGEABLE WITH SAID MOVABLE LEAF SPRING BLADES FOR SEQUENTIALLY DEFLECTING THE SAME SO THAT THE CONTACT MEANS THEREOF SEQUENTIALLY ENGAGE THE CONTACTS OF 